Air bag systems, or supplemental inflatable restraint systems, are commonplace in nearly all of the motor vehicles of today to protect occupants from serious injury upon collision or roll-over of their vehicles. With the present consumer interest quite high for additional features in new vehicles, air bag systems have proliferated inside the car such that they may deploy in nearly any direction and from nearly any surface. While air bag systems were originally integrated into the hub of the steering column for forward impact protection of the driver and into the instrument panel for similar protection for the front seat passengers, they may now be found integrated into seats and door panels for side protection, and integrated into headliners, pillar trim and quarter panels for roll-over protection. Additional locations may include air bags for knee protection by deploying from below the instrument panel, or air bags built into the back of the front seats to protect rear seated passengers, and even air bags integrated into the shoulder belts which are used for primary occupant protection.
For example, U.S. Pat. No. 6,102,435 to TRW Vehicle Safety Systems, Inc., entitled “Vehicle Headliner with Inflatable Side Curtain” is directed at a headliner assembly including an inflatable vehicle occupant protection device which is supported behind a door which hinges open upon bag inflation. U.S. Pat. No. 5,540,459 to Ford Motor Company, entitled “Roof Rail Mounted Air Bag Assembly” is directed at an inflatable restraint device having a trim cover which deflects away at its lower edge when an air bag opens downward from the roof side rail and between the occupant seat, the door and the window of the vehicle. U.S. Pat. No. 6,152,482 to Ford Global Technologies, Inc., entitled “Vehicle Inflatable Restraint System Trim with Trim Deploying Module” is directed at an inflatable restraint module mounted longitudinally adjacent a roof rail which when activated causes a flap member to operatively force a headliner assembly over a pillar trim piece to route the inflatable restraint past the pillar trim. U.S. Pat. No. 6,059,311 to Breed Automotive Technologies, entitled “Pillar-Mounted Side Impact and Rollover Air Bag” is directed at a side impact and crash protection and roll-over system comprising a web guide attachable to a pillar of a vehicle, a seatbelt system and an air bag assembly stored adjacent the web guide which when inflated is positioned adjacent the pillar. U.S. Pat. No. 5,531,470 to Joalto Design Inc., entitled “Side Air Bag Incorporated in Vehicle Outer Armrest” is directed at a vehicle side impact air bag system wherein the air bag is located in an outboard armrest which is pivotably attached to a vehicle seat. Upon deployment, a cover panel located over the armrest hinges along its bottom edge to allow the air bag to upwardly expand without restriction. These air bag systems ail include some sort of cover which is integrated into the surrounding vehicle trim to prevent tampering with the air bag or the mechanism that causes the air bag to deploy and which further hinges or deflects to allow proper bag deployment. These covers generally comprise an outer cover skin and a rigid door substrate, sometimes separated by a foam layer.
As these safety devices have become accepted and more popular, it has become common to conceal the presence of the air bag and its inflating apparatus by providing a cover which is indistinguishable from the surrounding plastic trim (commonly known as the invisible or hidden air bag door). Thus, the aesthetics of the interior are enhanced and the reminder of the presence of the safety equipment is minimized.
As the locations for the air bag systems have proliferated, the need for different types of materials to cover the air bag systems and economically integrate into the surrounding interior trim package has been recognized. Generally, in cars, the materials used above the “belt line” are desirably softer in surface hardness while below the “belt line” where scuffing is more prevalent, hard injection molded plastics may be more preferentially employed
Originally, air bag cover outer skins were of a soft thermoplastic (polyvinyl chloride, thermoplastic olefin or elastomer, thermoplastic urethane, etc.). Since seats, headliners, door panels and pillars are often fabric covered, particularly in European cars, there has been a recent focus on developing fabric or textile materials as candidates for the outer surface of air bag covers which might meet the demanding aesthetic and functional requirements.
One construction of a fabric covered air bag door that employs a “peel back” method is disclosed in U.S. Pat. No. 6,050,595 commonly assigned to the assignee of the present invention. The '595 patent is directed at an air bag closure assembly comprising a trim member including a panel and a skin, wherein the skin is supported on the outer surface of the door and trim member panel and whereupon air bag inflation the front edge of the door is pivoted away from the opening around the hinge to provide a path for air bag deployment through the panel. The skin is at least partially separable from at least a portion of the panel outer surface that extends laterally outward from the side edges of the door and from the front edge of the door to a front edge of the skin adjacent the front edge of the door, the skin delaminating when the door carries the skin outwardly and lifts the skin from the panel outer surface as the air bag inflates and forces the door to an open position, the skin forming a skin tent over the door, the skin tent having a skin tent opening formed by the delaminated front edge of the skin thus providing an exit for the deploying air bag.
To provide deployment of the airbag without fragmentation of the cover and to ensure tearing of the cover skin and reliable opening of the air bag door in combination with concealment of the door and door opening, it has been found that pre-weakening of the cover skin in a pattern that approximates the air bag door opening is desired. This pre-weakening is has been accomplished by reducing the cross-section (i.e. thickness) of the cover skin and door substrate locally to form a tear seam. This may be accomplished by molding a groove into the door substrate and into the inside of the cover skin or by the use of a laser or knife to form a groove (slots, perforations, etc.) in the substrate layer which may extend into a foam and/or cover layer.
For example, European Patent Application EP 1216894A1 to Delphi Automotive, entitled “Instrument Panel with Integral Hidden Door Cover and Method of In-Process Manufacture Thereof” is directed at forming a score on the backside of a preferably vacuum formed instrument panel skin with a cylinder-activated blade to create a weakened region in the pattern of an air bag door seam. The skin is then foamed in place with a retainer. U.S. Pat. Nos. 5,421,608; 5,431,435; 5,447,328/RE 37,540; 5,564,731; 5,685,930; 5,783,016; 5,804,121; 5,902,428; 5,941,558; 5,961,143; 5,975,563; 6,050,595; 6,131,945; 6,203,056; 6,402,189; 6,457,738; 6,460,880; and U.S. application Ser. Nos. 10/286,251; 60/367,924; 60/368,418; and 60/411,548; commonly assigned to the assignee of the present invention and included herein by reference, are directed at air bag doors which are contained in or molded as part of a larger panel and which contain weakened areas to allow predictable deployment of an air bag through the panel.
While examples of this technology are common with the flexible skin materials, it has not been fully demonstrated that weakening of a fabric layer for a cover can be similarly accomplished. Use of a laser beam to cut fabric is known. U.S. Pat. No. 6,283,001 B1, entitled “Facility for Cutting Fabric . . . ” recites “in a preferred embodiment, the cutting head is a laser cutting beam. This type of cutting head possesses a laser beam source and a corresponding focusing optical system, which focuses the laser beam on the fabric band. To avoid undesirable oxidation, an additional protective gas jet can be provided, which pushes away from the cutting position the oxygen containing air by means of inert gases, i.e.: nitrogen or other inactive gases. Especially, where artificial fiber containing textiles are concerned, a fume removal system can be provided, which, during the cutting, removes the vaporized substance in order to uphold the required working place environmental regulations (MAK-values). Attention is also directed to U.S. Pat. No. 6,140,602, entitled “Marking of Fabrics and Other Materials Using A Laser” to Technolines LLC, which discloses a method for imparting laser induced patterns and other designs on thin fabrics and leathers.
Regarding specific references to weakening cover layers in air bag door systems, U.S. Pat. Nos. 6,294,124 B1 and 5,744,776 to Bauer of TIP Engineering suggest the use of a laser to weaken the backside of a “cover layer” by cutting through the substrate and partially through the cover layer. FIG. 13 therein is said to illustrate “the use of a laser applied to a cosmetic cover layer 92 shown as a textile material as might be used with a side impact air bag system, which has a scrim backing layer 94 bonded thereto. The laser scored groove 95 penetrates completely through the backing scrim 94 and partially through the textile layer 92.” Published United States Application No. 20022/0050046 A1 also to TIP Engineering, is entitled “Process for Manufacturing an Automotive Trim Piece Preweakened To Form An Air Bag Deployment Opening”. This application recites a process for constructing a trim piece having a section pre-weakened in a pattern to allow formation of one or more deployment doors, whereby a stiff substrate is formed having one or more integral doors with a predetermined gap between adjacent portions and one or more cover layers are laid over the substrate panel and extend across the predetermined gaps. Pre-weakening of the overlaying cover layers is accomplished by laser scoring portions of the inside of the cover layers along the gap.
Therefore, while the field not surprisingly has many disclosures charting off in a variety of different directions to provide a cosmetically appealing and functional air bag deployment system, there still exists a need in the art for fabric or textile covered trim panels to be used as air bag covers, wherein the fabric as well as the substrate is efficiently pre-weakened to allow predictable deployment of the air bag and tearing of outer cover layer.